1. Field of the Invention
The present invention relates to a position detecting method of detecting a pattern position of a detection target.
2. Description of Related Art
Methods of verifying such as a person's face based on an acquired image have been used. One such method that has been proposed, for example, includes normalizing a stored registered image, extracting a feature of the image, and projecting the extracted feature to an identification space with high identifiability. The method further includes similarly normalizing an image to be verified, extracting a feature of the image, projecting the extracted feature to a similar identification space, comparing the features to output a verification score, and performing verification according to this score (see, Japanese Unexamined Patent Application Publication No. 2006-338092, for example).
Other methods for identifying a feature of an image that has been proposed includes dividing of the image. For example, there has been proposed a method of dividing a single original image into nine pieces of 14×18 pixels (252 dimensions), taking a partial image of each size as a feature vector, and performing an analysis for identifying the partial image using a learned sample. This method allows identification with at least a certain degree of accuracy of the learned sample for performing identification of an image, as the number of the dimensions of the feature of an image largely decreases down to 252 as compared to the original image (see Japanese Unexamined Patent Application Publication No. 2004-192603, for example).
Further, there are industrial machines and the like that processes an image of an attachment component or a processed component to perform positioning the component. As one example, such a machine provides a target as a recognition pattern and a positional reference at a position around a semiconductor chip, acquires image data of the target provided on the semiconductor chip using an ITV camera, compares the acquired image with an image of target data that has been previously set, and aligns the position of the semiconductor chip by matching the images (see Japanese Unexamined Patent Application Publication No. H07-193093, for example).
When a position of a component is aligned according to the conventional technique described in Japanese Unexamined Patent Application Publication No. H07-193093, it is necessary to first acquire the image of the component using a camera because the positional alignment is performed by providing a target at a predetermined position around the component as a positional reference and matching an image of the target acquired by a camera with an image of target data that has been previously set. However, there is a case in which a clear image cannot be acquired due to a lighting condition around the component, or an image of the target cannot be acquired for some reason. There is also a case in which accuracy in positioning of the component is reduced when the image of the target is not clear, or the position of the component cannot be determined when the image of the target cannot be acquired, and therefore the assembling machine has to be stopped.
Therefore, as described in Japanese Unexamined Patent Application Publications No. 2006-338092 and No. 2004-192603, more industrial machines have come to employ a method of performing positional alignment of a component by comparing a feature of a component image to determine the component and detecting a position of the component based on the result of the comparison. According to this method, a component does not have to be provided with a target, it is possible to recognize and align a position of the component without a previously provided target, and the component can be recognized and its position can be aligned based on an entire image even if an image around the component is unclear. Therefore, recognition and alignment of the component can be performed more stably and accurately. Additionally, a method of dividing an image is often used so that an image can be identified with less learned samples.
However, it takes long to process the image in order to determine a component based on an acquired image. An industrial machine is required to perform positioning of a component in a short time, and a higher processing speed is demanded as compared to a case of recognizing an individual person based on an image of the person's face. For example, an application of such a method to industrial machines has been restricted because when processing an image by dividing the image, processing time for combining detection scores of the divided images, or for determining which one of the divided images is most suitable for determination and positioning of the component often takes long.